multipath
also: dm-multipath, Device Mapper multipath
A Linux kernel feature and software stack that manages multiple physical paths to the same storage device, automatically routing I/O traffic and providing failover when a path fails.
Multipath enables redundancy and load balancing for block storage by detecting and utilizing multiple independent routes (via different cables, network adapters, or HBAs) to reach a single logical storage device. If one path fails, I/O automatically continues on remaining paths without interrupting the application.
The Linux multipath implementation uses the Device Mapper to create a virtual device aggregating multiple physical paths. The multipathd daemon continuously monitors path health and updates the routing table, while the multipath command configures and manages these virtual devices.
Example: A server with two HBAs connected to a SAN storage array via separate switches will see four paths (2 HBAs × 2 switch connections). Multipath combines these into one logical device at /dev/mapper/mpatha, eliminating path fragmentation and ensuring high availability.